dilution water

synonym: diluent
https://doi.org/10.1351/goldbook.14588
Water used to dilute the test material in an aquatic toxicity test in order to prepare either different concentrations of a test chemical or different percentages of an effluent for the various test treatments.
Note: The water (negative) control in a test is prepared with dilution water only.
Source:
PAC, 2009, 81, 829. (Glossary of terms used in ecotoxicology (IUPAC Recommendations 2009)) on page 867 [Terms] [Paper]